The present invention relates to a coating method and a coating apparatus used for manufacturing stimulable phosphor plates, silver halide light-sensitive materials and magnetic recording materials.
For manufacturing a large quantity of recording materials such as stimulable phosphor plates, silver halide light-sensitive materials and magnetic recording materials, there are used coating processes for forming various types of layers having various types of functions and characteristics.
These layers to be formed have been highly required to be thin in thickness and to be small in dispersion in recent years, for raising performance of recording materials. Further, not only coating at high speed but also a loss of coating liquids in a small amount and coping with production for many types in small output of products have been required.
On the other hand, examples of a coating method and a coating apparatus laid open to public inspection lately include the following. TOKKAIHEI No. 8-206565, for example, discloses a technology to overcome the situation wherein a change of a chamber fluidity in an extrusion type coating apparatus makes it impossible for the ordinary extrusion type coating apparatus to distribute coating liquids evenly in the lateral direction, when a type of coating liquid with high viscosity is changed, or physical properties of liquids are changed. The technology is represented by a coating apparatus wherein a spare chamber is provided to be ahead of a chamber, then, a plurality of fluidity distribution valves are provided in the spare valve to adjust fluidity, and thereby, coating liquids are distributed evenly in the lateral direction of the coater to make a coating thickness to be uniform. Further, TOKKAIHEI No. 10-8003 discloses a coating method wherein a rotary screw-shaped object is provided in a liquid dam of two roll coaters, for improving fluidity of coating liquids, and coating is conducted while the screw-shaped object is rotated.
In the technologies mentioned above, a uniform coating thickness can be obtained for sure if adjustment is made properly, even when characteristics of a coating liquid are changed in the course of coating operations. However, adjustment of flow rate is complicated, and it is sometimes impossible to obtain a desired layer thickness and accuracy distribution for dispersion of the layer thickness, depending on the state of coating liquids, if the rate of aperture of the valve is constant from the beginning to the end of coating. In addition, an amount of loss of coating liquids is large because a chamber section is greater, compared with a former coating apparatus, valve adjustment requires a longer period of time at the start of coating, and amount of loss of coating liquids on that portion is large. Further, when conducting coating, if a shearing speed at a certain extent needs to be applied immediately before coating, there is caused a problem that coating quality is not satisfactory.
On that point, it is possible for the technology in the latter case to apply shearing speed to coating liquids and to coat while maintaining satisfactory characteristics of coating liquids. However, the basic system of that technology is not an extrusion type coating system, and it is difficult to obtain satisfactory coating quality in terms of accuracy of a coating thickness accordingly.
The invention has been achieved to solve the problems stated above.
Namely, an object of the invention is to provide a coating method and a coating apparatus wherein a coating thickness is uniform, a size of its dispersion is small, an amount of loss of coating liquids is extremely small, which makes cost reduction possible, a coated surface can be made to be excellent because shearing speed can be applied to coating liquids immediately before coating, and space saving can be attained because a coater section is of an integral type.
The objects of the invention are attained by employing either one of the following methods and structures.
(1-1) An extruding coating method comprises steps of:
feeding a coating liquid into a coating liquid reservoir section provided with a slit having a slit width; and
extruding the coating liquid through the slit so as to conduct coating, wherein the coating liquid is extruded through the slit by pushing the coating liquid in the coating liquid reservoir toward all over the slit width by a piston.
(1-2) In the extruding coating method of (1-1), the extruding coating method further comprises a step of:
applying a shearing speed to the coating liquid in the coating liquid reservoir section.
(1-3) In the extruding coating method of (1-1), the piston has a plane section which is parallel to the slit and has a length not shorter than the slit width and the piston pushes the coating liquid with the plane section.
(1-4) In the extruding coating method of (1-1), the piston pushes the coating liquid at a constant speed.
(1-5) In the extruding coating method of (1-1), a concentration of solid components in the coating liquid is 20 vol % or more.
(1-6) An extruding coating apparatus, comprises:
a coating solution feeding section to feed a coating liquid;
a coating solution reservoir section provided with a slit having a slit width and to store the coating liquid fed by the coating liquid feeding section; and
a piston to push the coating liquid in the coating liquid reservoir section toward all over the slit width so as to extrude the coating liquid through the slit.
(1-7) In the extruding coating apparatus of (1-6), the extruding coating apparatus further comprises:
a shearing speed applicator to apply an equal shearing speed all over the slit width to the coating liquid in the coating liquid reservoir section.
(1-8) In the extruding coating apparatus of (1-7), the shearing speed applicator is a rotatable roller provided in the vicinity of the slit in the coating liquid reservoir section.
(1-9) In the extruding coating apparatus of (1-7), the shearing speed applicator is a ultrasonic wave emitting device to emit ultrasonic waves toward the coating liquid in the coating liquid reservoir section.
(1-10) In the extruding coating apparatus of (1-6), the piston has a plane section which is parallel to the slit and has a length not shorter than the slit width and the piston pushes the coating liquid with the plane section.
(1-11) In the extruding coating apparatus of (1-6), the piston pushes the coating liquid at a constant speed.
(1-12) In the extruding coating apparatus of (1-6), a concentration of solid components in the coating liquid is 20 vol % or more.
(1-13) A coater, comprises:
a coating solution reservoir section provided with a slit having a slit width and to store a coating liquid; and
a piston to push the coating liquid in the coating liquid reservoir section toward all over the slit width so as to extrude the coating liquid through the slit.
Further, the above object may be attained by the following preferable method and apparatus.
(2-1) An extrusion type coating method for coating by distributing coating liquids injected in a coating liquid reservoir section having a slit with a desired width to cover a desired width, wherein a pressurization ram forces in and conveys coating liquids through the entire area of the slit in its width direction for coating.
(2-2) An extrusion type coating apparatus provided with a coating liquid reservoir section having a slit with a desired width and a pressurization ram for forcing in and conveying coating liquids through the entire area of the slit in its width direction, wherein coating liquids injected in the coating liquid reservoir section are distributed uniformly over the desired width for coating.
(2-3) The extrusion type coating apparatus according to (2-2), wherein a rotary roll is provided in the vicinity of the slit having the desired width in the coating liquid reservoir section of the extrusion type coating apparatus, and there is proved a mechanism that applies to coating liquids shearing speed that is uniform in the direction of the width.
The invention relates to an extrusion type coating method and an extrusion type coating apparatus. The extrusion type coating apparatus is a coating apparatus which can coat uniformly on a support an amount of coating liquids equivalent to a prescribed coating thickness, and it is a coating system excellent in terms of layer thickness distribution and coating stability and it is a typical method of the measuring coating system, although it requires mechanical accuracy. A coater in this system is a part of the coating apparatus, and it is a portion where the coating liquid to be coated on a support finally is ejected.